Down-draft unit heater



Aug. 25, 1931. c. c. CARSON DOWN DRAFT UNIT HEATER Filed May 31, 1930 2Sheets-Sheet l INVENTOR 5mm? 6: BY 96 m ATTORNEYS Aug. 25, 1931.

c. c. CARSON DOWN DRAFT UNIT HEATER Filed May 31. 1930 2 Sheets-Sheet 2QNVENTQR 6:654:00? BY/' 7 @W MQ @Q QQ a /film ATTORNEYS Patented Aug.25, 1931 UNITED STATES PATENT oFncE CLIFFORD C. CARSON, OF CHICAGO,ILLINOIS Down-11mm UNIT HEATER Application filed Kay 31, 1930. SerialNo. 458,301.

This invention relates to unit heaters of the suspension type and, amongother objects, mm to provide an improved down- Fig. 1 is a sideelevation of a direct-fired,

suspension type heater embodying the in- 2 vention; Fig. 2 is a bottomplan view of the heater shown in Fig. 1; Fig. 3 is a central sectionalview; and Fig. 4 is a section taken on the line 4-4 of Fig. 3.

Referring particularly '-to the drawings, the heater is shown as'havingprovision to be suspended from roof joists or the like in a building orlarge room and is adapted to be arranged at any convenient height abovethe floor, the idea being to conserve the floor space, and to dischargethe. heated air downwardly so as to break up the cold air film adjacentto the floor and cause the heated air to circulate in the space to beheated. In this example, the heater is of the direct fired type and isada ted to utilize any suitable fluid fuel, eit er liquid or gaseous;

I However, it will be understood that the invention is not limited todirect fired heater ,units.

' Referring to Figs. 1 and 3, the heater is .there shown as having sheetmetal casing --w alls 10 secured to box headers 11 and 12 at theoppositenends to which groups of return fire tubes 13am connected. Thebox header 12 is here shownas' having a fire box portion 14 in the lowerpart and the fuel is supplied to the fire box through .a serles ofnozzles 15'. The arrangement is such that I either liquid or gaseousfuel may be utilized without making any alterations. The productsofcombustion pass through the lower group of tubes shown in Figs. 3 and 1to the return smoke or box header 11; thence through the upper group oftubes into the upper portion of the fire-box header 12. above a divisionplate or partition 16 and out through a suitable stack 17. In thisinstance, the tubes 13 are welded or otherwise secured in suitableopenings in tube sheets 18 and cast or sheet metal boxes are bolted orotherwise suitably secured to the plates. However, the box headers mayhave hand hole openings to afford access to the 5 ends of the firetubes.

The upper end of the casing defined by the side walls and smoke boxes orheaders, is open to admit air to circulate through the casing about thefire tubes which are conveniently arranged in staggered relation.

To the lower inside edges of the fire tube sheets 18 and the side walls10 of the casing is connected a sheet metal conduit 19 having a reducedlower end through which the air is adapted to be discharged downwardlyafter being'heated by the fire tubes. Below the lower end of thisconduit is arrangeda fan 20 of the impeller type which is driven by amotor 21 supported on suitable arms so or brackets 22. The arms areconveniently made of tubular stock and are likewise connected to the boxheader and the side walls of the heater casing. In this instance, the

"upper ends of the arms and the outlet conduit 19 are secured to thelower portion of the heater by meansof bolts passing through suitableflanges in the box headers 11 and 12 and also through the tube sheets18. The

same set of belts or rivets, as the case may I be, are here used to'secure both members to thecasing. The arms 22 extend radially andhorizontally from the supporting collar for the motor 21 and on thesearms is secured a' bell-shaped sheet metal conduit or outlet nozzle 23having radial openings through which the arms are inserted before beingconnected to the motor supporting collar; The arrangement is such thatthe heated air induced by the fan 20 is disbracket members 22 adjacentto the motor casing.

In Fig. 3, the blades of the fan are shown as extending beyond thecircular edge of the lower end of the conduit 19. An annular sheet metalwall 25 is shown as being secured to the arms 22and spaced from theouter walls of the conduit 19 and the nozzle 23. The lower end of thissheet metal member is flared outwardly. The arrangement is such that theextended ends of the blades of the fan 20 discharge an umbrellashapedcurtain of air through the annular passage 26 between the wall 25 andthe bellshaped nozzle 23, the flared lower ends of the nozzle and thewall being shaped some what like a Venturi nozzle, This curtain of airis sucked in through the annular space around the upper portionof theconduit 19 and between the reduced lower end portion and a horizontalannular flange 27 on the sheet metal wall 25. Since the peripheral speedof the outer ends of the fan blades is much greater than that of theinner end portions, and the annular passage 26 for the air curtain is ofless cross sectional area than the outlet passage for the heated air,

the velocity of the curtain of air is vconsiderably greater than thevelocity of the dis- 7 charging heated air.

It will be observed that the curtain of air is discharged at an angle tothe vertical.

. This angle is determined largely by the height at which the heater issuspended and the operating conditions. The idea is to have the curtainenvelop the stream of.

heated air and flatten out horizontally at or near the breathing line.The heated air is confined thereby to circulate below the breathingline. It is contemplatedthat the angulari-ty of the discharging nozzlemay be between 15 and 45 to the vertical. The shape of the'flared orbell-shaped nozzle 23 and of the sheet metal housing or wall 25 may bemade to suit the conditions under which the heater is to work.

From the foregoing description, it will be observed that the intake airfor the heater is admitted through the upper end of the casing and heatis initially absorbed by it from the upper group of fire tubes. Thesefire tubes are somewhat cooler than are the tubes of the lower group. Asthe air passes around the tubes of the lower group, which are hottest,it absorbs a finalincrement of heat. By this arrangement of tubes, thetemperature differencebetweenth'e air and the heating surfaces is'maintained more nearly constant,

thus providing a. very high heating efli ciency. Moreover, the intakeair coming from the upper portion "of the room or building is somewhatwarmer than is the air adjacent to the floor and this further economizeswith fuel. Furthermore, the umbrella curtain,of air'is somewhat warmerthan it would be if taken from a point nearer the floor. Hence, thetemperature difference between the curtain and the discharging heatedair is not very great. Since the heater is of the down-draft type, airwill circulate through it even when the fan is not running and therebyprevent the fire tubes from being burned 'out. The discharge nozzle andthe casing will act as a stack for the air and'a natural draft will beset up. Of course, it is contemplated that any convenient automaticcontrolling apparatus may be employed in connection with the iuelburners and the motor for driving the While the novel apparatus forconfining a vertical stream of heated air by means of anumbrella-shapedor frusto-conical curmin. of high velocity air is shownas being connected to the lower end ofa direct fired heater, it is to beunderstood that it may be used in combination with the ordinary steam orhot water units now commonly employed. The direct fired unit is welladapted for use in sections of the country where natural and/orartificial gas are available at low.

rates. Moreover, such heaters can be employed advantageously where crudeoil is used as fuel.

Obviously, the present invention is not restricted to the particularembodimentthereof herein shown and described. Moreover, it is notindispensable that all the features of the invention be used conjointly,since they may be employed advantageously in various combinations andsub-combinations.

What is claimed is: p 1. A down-draft unit heater comprising air heatingmeans; a discharge conduit connected to discharge heated air downwardly;

and means to discharge an enveloping curtain of air around and above thedischarging heated air.

2. A down-draft unit heater comprising,

connected to discharge the heated air down wardly and means to dischargea frustoconical curtain of air at a relatively high velocity around thedischarging heated air.

4. A unit heater of the character described comprising, in. combinatimr,direct fired heating' means; a casing for the heating means; a. fansupported by the heater .and con-' nected to discharge heated airdownwardly from the casing; and means for directing an viiumbrella-shaped curtain of air downwardly and at an angle to thevertical around the discharging heated air.

5. In a unit heater. of the character described, a dischargenozzle forheated air arran "ed to direct the'air downwardly; a

fan or blowing the air. through said nozzle' an annular conduitsurrounding said di charge nozzle; and a single. fan arranged tndischarge heated airthrough said nozzle. 1 and relatively cold airthrough said conduit heated air; a fan between the conduit and saidnozzle; an annular passage surrounding said nozzle; and means todischarge an umbrella-shaped curtain of air through said annular conduitaround the discharging heated air.

7. A unit heater ofthe; character described comprising, in combination,a horizontal fire tube 'heater' unit havingan, as-'- sociated fire box;an air discharge conduit connected to the lower end of the-heater unit;a propeller .fan below the discharge conduit; a bell-shaped nozzlesupported below the fan; a sheet metal wall spaced from the bell-sha dnozzle and roviding an annular con uit; the blades oi said fan extendinginto said annular conduit and ar- 4 ranged to discharge air therethrougharound the discharging heated air so as to confine the heated air tocirculate in the space be- "low the breathing line it has givenup asubstantial portion of its heat. 5 8. A unit heater of the characterdescribed comprising, in combinlation,- a horizontal direct fired,fireltube heater unit having a conduit connected'to its 'lower side andarranged to discharge air downwardly therefrom; a fan arranged todischarge air through said conduit; a sheet metal wall surrounding saidconduit and providing an annular passage for relatively cool airaroundthe'discharge end of said conduit; and means to create a highvelocity stream of .airthrough said annular passage so as to; dischargearound the discharging heated air and confine it to circulate in thelower po -tic pf the space to, be heated it has 9. In a unit neater ofthe character'de scribed, a do'wn-drait heater element; a plurality ofsupporting arms connected tosaid 'heaterelement; a motor supported bysaid arms; a fan driven by said motor; aver;

tical-discharge nozzle below said fan; and means associated with saidfan to discharge an umbrella-shaped curtain of relatively cold airaround the heated air discharged by said fan so as to confine the heatedair to circulate in the lower portion of the space to be heated until ithas given up asubstantial portion iif its heat.

10. In a unit heater of the character described, a down-draft heaterelement a vertical discharge conduit connected to the heater; a fan,below the heater element; a fan' motor supported in the conduit belowthe fan; and a shield in the conduit be tween the fan and the motor toprotect the motor from the influence of the discharging heated air. I v

In testimony,'th at I claim the foregoing as my own, I have heretoaffixed my signature.

' CLIFFORD c. CARSON.

